Carbohydrate transferases are responsible for synthesis of cell surface glycoproteins and glycolipids. None of the enzymes were purified and their molecular properties were obscure. Recently two carbohydrate transferases, i.e. an N-acetylgalactosaminyl transferase, which synthesises the blood group A-substance (A-enzyme), and a galactosyltransferase, which produces the blood group B-substance (B-enzyme) were first purified to homogeneity in this laboratory. Human plasma and red cell membrane contain many carbohydrate transferases; some of these are responsible for synthesis of specific blood group substances (A1, A2, B,H), and others play a role in synthesis of glycoproteins and glycolipids. The objective of the proposed project is to determine: 1) the relationship between structure and function of blood group A-enzyme and B-enzyme and an enzymatically inactive, but immunologically cross-reactive, protein in O-plasma; 2) the molecular properties and immunologic characteristics of other carbohydratetransferases in human blood; and 3) the underlying genetic mechanism of expression of common (ABO, MN) and rare (Am, Ax, Bombay) blood types. The project consists of the following studies: 1) purification and structural characterization of blood group A1-enzyme, A2-enzyme and B-enzyme and an enzymatically inactive but immunologically cross-reactive protein existing in O-plasma; 2) purification and study of enzymatic, chemical and immunologic characteristics of N-acetylgalactosaminyltransferase from Am and Ax plasma, and examination of membrane components in A2, Ax and Am; 3) purification and chemical and immunologic characterization of other carbohydrate transferases.